Stacks of semiconductor chips can be produced by a procedure in which contact areas are in each case produced at the top sides of the semiconductor chips in a topmost metal layer of the wiring planes, which contact areas are covered with a passivation, a plated-through hole is in each case produced through the passivation and an electrically conductive connection is produced between the plated-through hole and an associated interconnect applied on the top side. The chips are arranged with the relevant top sides facing one another and opposite one another in such a way that the interconnects to be connected to one another are located one on top of the other. The interconnects are permanently connected to one another using diffusion soldering known per se, in particular the SOLID process. In order to produce the soldered connection, a thin solder layer is applied to the relevant interconnects of at least one of the semiconductor chips.
This production method affords the advantage, inter alia, of an additional relatively thin metal plane in the connecting zone (interface) of the two chips which can be used for wiring purposes. By way of example, in this interconnect plane which is provided only for connecting the chips, a rewiring of the chip contacts may be performed or the chips may be contact-connected by means of this plane to interconnects suitable for high frequencies (strip lines).
The connecting plane is formed in a single layer, however, so that the interconnects present therein cannot be bridged. A bridging of the interconnects present in the connecting plane is only possible if suitable electrically conductive connections are provided in one of the metallization planes of the wiring of the semiconductor chips themselves, which connections, via the plated-through holes to the interconnects connected to one another by means of diffusion soldering, short-circuit the interconnects. This requires two plated-through holes (vias) and a metal bridge in the topmost metallization plane of one of the chips that are to be connected to one another. A corresponding adaptation in the design of the metallization planes is therefore required as early as in the production of the chip.